Girls lift tractor off dad: Two sisters in Oregon lifted a 3,000-pound tractor off of their father after the tractor flipped and pinned him to the ground. (Photo: Flickr/Marion Doss)

Sisters Haylee Smith, 14, and Hannah Smith, 16, lifted a 3,000-pound tractor off of their father after the tractor flipped over on top him. New York Daily News reports that on Monday, April 1, 36-year-old Jeff Smith of Lebanon, Ore., was operating his tractor to remove a stump from his yard when the machine flipped, pinning him to the ground. He cried out for help.

Oregon Daughters Come To Rescue

That's when Smith's two daughters came from school and heard their dad screaming for help. The teenage girls rushed over and lifted the 3,000-pound tractor just high enough that Jeff Smith was able to get his chest out from under the tractor. The girls then called a neighbor over, who helped get Smith fully out from under the flipped tractor.

Jeff Smith sustained minor injuries from the accident, including a broken wrist.

Hannah Smith, the older of the two girls, told the Albany Democrat-Herald that she felt a rush of adrenaline when she lifted the 3,000-pound tractor.

That's a heavy load, and not one that many people can say they've ever lifted. In fact, the current world record for most weight dead-lifted is 1,015 pounds, held by Icelandic strongman Benedikt Magnússon. If one of the world's strongest men can lift less than half the weight of the tractor that trapped Ben Smith, how, then, were the teen sisters able to lift a 3,000-pound tractor off of their dad? Where did such superhuman strength come from?

Wise explains that when under acute stress, the human body can prepare itself for sustained, vigorous action by releasing cortisol and adrenaline into the blood stream by way of the adrenal gland. In such cases, the heart races and blood pressure skyrockets, quickly pumping oxygen and energy to the muscles.

"It's the biological equivalent of opening the throttle of an engine," Wise wrote.

Penn State professor of kinesiology Vladimir Zatsiorsky, who studies the biomechanics of weightlifting, found that an ordinary person can tap into about 65 percent of their absolute power - defined as the force our muscles can theoretically apply - during a weightlifting session, but that a trained weightlifter can exert more than 80 percent. That's why major events like the Olympics, where competition is heated and stake are highest, are prime time for record breaking.

"But there's a limit to how fast and how strong fear can make us," Wise wrote. "Zatsiorsky's work ... suggests that while fear can indeed motivate us to approach more closely to our absolute power level than even the fiercest competition, there's no way to exceed it." He also pointed out that during such extreme adrenaline rushes as the kind that allow people to do things they normally would not be able to do, the body's ability to feel pain is also softened - a phenomenon known as analgesia.

"Under intense pressure-whether it's a bodybuilding competition, a kid trapped under a car, or an attacking bear-you just won't feel that pain," he wrote.

The day after Hannah and Hayley Smith's superhuman act, Hannah Smith said she definitely felt worse off.